[EPIC] Multi-dimensional, heterogeneous data container

### Is this a duplicate?

- [x] I confirmed there appear to be no [duplicate issues](https://github.com/NVIDIA/cccl/issues) for this request and that I agree to the [Code of Conduct](CODE_OF_CONDUCT.md)

### Area

libcu++

### Is your feature request related to a problem? Please describe.

`mdspan` greatly simplifies working with multi-dimensional tensors. On the other hand, `mdspan` requires that pre-allocated memory and acts as a view on top of it.

### Describe the solution you'd like

Provide ``

### Describe alternatives you've considered

_No response_

### Additional context

_No response_